inflexibility vs unmanageableness

inflexibility

noun
  • The quality or state of being inflexible, or not capable of being bent or changed; unyielding stiffness 

unmanageableness

noun
  • The state or quality of being unmanageable. 

How often have the words inflexibility and unmanageableness occurred in a corpus of books? (source: Google Ngram Viewer )